The invention relates to a wiper system for vehicles as generically defined and to a method for operating a wiper lever linkage of a wiper system for vehicles.
A known wiper system has a pivot lever that can be pivoted freely about a stationary shaft, and a wiper arm provided with a wiper element is secured to the pivot lever. Because of this design, the wiper arm takes a circular path, which means only a small swept field, which in many cases does not meet requirements.
A wiper system is also known that has a four-bar wiper lever linkage which includes first and second pivot levers that are each coupled in a manner fixed against relative rotation to a stationary shaft and connected in articulated fashion to a coupling element. A wiper arm provided with a wiping element is secured to the coupling element and upon pivoting of the pivot lever executes a reciprocating-pivoting motion, which leads to an enlargement of the swept field. A disadvantage in the known wiper system is the large installation space required for the wiper lever linkage, space that if the wiper system is to be used to clean a windshield of a motor vehicle must be made available in the region of the front end of the vehicle. However, there is little space in the front-end region of the motor vehicle, and in future vehicles there will be even less, since the proportion of the length of the interior to the total length of the motor vehicle is becoming greater and greater. It is also found that the swept field of the four-bar wiper lever linkage is not large enough to meet legal requirements, or increasing demands for comfort and safety, given the large window surfaces planned for vehicles in the future in particular.
The wiper system of the invention has the advantage over the prior art that for the same installation space, a markedly longer stroke and thus a larger swept field can be achieved with the wiper lever linkage than in the known wiper system with the four-bar wiper lever linkage. It is understood that it is also possible to design a wiper lever linkage that, for at least essentially the same-sized swept field or essentially the same feasible stroke length in the known four-bar wiper lever linkage, has a smaller installation space. To achieve a large swept field with a compact design of the wiper lever linkage, it is provided in the wiper system of the invention that the coupling element is embodied in multiple parts and has a first coupling part and a second coupling part, which are coupled to one another with the aid of a joint. A five-bar wiper lever linkage is thus created in which an exact control of the stroke is possible.
In an especially advantageous exemplary embodiment of the wiper system, the wiper lever linkage is assigned a drive device, which has first and second drive cranks, of which the first drive crank is coupled in a manner fixed against relative rotation to the first shaft, to which the first pivot lever is also secured, and the second drive crank is coupled in a manner fixed against relative rotation to the second shaft, on which the second is retained. In other words, the first and second shafts can each be subjected to a driving or braking moment that is transmitted via the pivot levers to the wiper lever linkage.
In an advantageous variant embodiment, the first and second drive cranks are connected to one another in articulated fashion with the aid of a coupling member. As a result, the motions of the first and second drive cranks and thus also of the first and second pivot levers are dependent on one another, and hence the degree of freedom of the wiper lever linkage, provided by the additional joint between the first coupling part and the second coupling part, is balanced or compensated for. To adapt the motions of the two drive cranks to one another, in another variant embodiment the first and second drive cranks are each connected in articulated fashion to an engine crank, and the engine cranks in turn are coupled to one another in such a way that their oscillating motions are adapted exactly to one another. In both variant embodiments, for controlling the pivoting motion of the drive cranks and thus also of the first and second pivot levers, the pivot angle of the second drive crank is adjustable freely, independently of the multi-part coupling element that connects the pivot levers to one another, since the first and second coupling parts of the coupling element are connected to one another in articulated fashion, thus providing one additional degree of freedom for the polygonal joint. Adjusting the pivot angle of the second drive crank can be done for instance by changing the length of the coupling member.
Further advantageous features of the wiper system will become apparent from the other dependent claims.
The subject of the invention also pertains to a method for driving a wiper lever linkage of a wiper system for vehicles, having the characteristics of claim 8, in which it is provided that the first and second drive cranks, during one wiping cycle, are pivoted out of an outset position of the wiper lever linkage in the same direction until they reach an extended position, in which the coupling member, which can for instance be in rod form, and the first drive crank are aligned with one another. In the further course of the wiping cycle, in which the wiper lever linkage is displaced out of the extended position to a turning point position, the first drive crank is pivoted onward in the same direction and the second drive crank is pivoted onward in the opposite direction. To optimize the course of motion of the wiper lever linkage, it is designed such that during one wiping cycle, the first drive crank has two turning positions and the second drive crank has three turning positions, in each of which a reversal of the pivoting direction takes place.
Further advantageous embodiments of the method will become apparent from the other dependent claims.